Mica-grinding machine.



J T. GRIFFIN. MICA GRINDING MACHINE.

APPLICATION FILED JULY 28,1916- 1,263,057. Patented Apr. 16, 1918.

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APPLICATION FILED JULY 23.1916.

Patented A r. 16, 1918.

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JAMES T. GRIFFIN, OF OAK PARK, ILLINOIS, ASSIGNOR T0 WESTERN ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

ERICA-GRINDING MACHINE.

Specification of Letters Patent.

Patented Apr. 16, 1918.

Application filed July 28, 1916. Serial No. 111,768.

To all whom it may concern:

Be it known that I, JAMEs'T. GRIFFIN, a citizen of the United States, residing at Oak Park, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Mica-Grinding Machines, of which the following is a full, clear, concise, and exact description.

This invention relates to a mica grinding machine, and more particularly to a machine of this type for grinding the mica insulators used for air gaps in high potential protective devices.

In the electrical art, sheet mica is used extensively as an insulator. For example, lightning arresters such as are used in telephony are made by interposing a mica sheet between two carbon blocks to provide an air gap of predetermined length. In order to avoid having one part of a telephone system less protected than another and to insure a uniform standard of protection in general, it is essential that the mica dielectrics be of uniform thickness. The mica sheets used are very thin in such cases, having a thickness of about .005 inches for example. The permissible variation above or below this figure is about .00025.

It has been very difficult heretofore to ob' tain the desired uniformity without considerable wast of material, as the practice has been to split ofi the mica sheets from a block of mica along the natural line of cleavage, using a needle. The sheets are thereafter measured, resplit and remeasured until they fall within the required limits. Those that prove to be too thin are discarded. The object of the present invention is to rovide a machine which automatically feeds the'thin mica sheets to a grinding wheel whereby they may be ground accurately to the desired thickness. The sheets supplied to the machine are somewhat thicker than the finished product but much less care and accuracy is required in splitting oif blanks to be supplied to the machine than in attempting to split the sheet to almost the exact thickness desired.

In the accompanying drawings a machine is illustrated which embodies the invention.

Figure 1 is a front elevational view thereof.

Fig. 2 is a sectional view on plane 2-2, Fig. 1.

Fig. 3 is a plan view.

Fig. 4 is an enlarged plan view of the disk supporting table.

Fig. 5 is a sectional view on plane 55, Fig. 4.

Fig. 6 is an enlarged plan view of the mica feeding device.

Fig. 7 is a front view of said device, and

Fig. 8 is an enlarged sectional view on plane 88, Fig. 5.

The supporting frame of the machine comprises a table 10 on which is mounted a suitable base 11 in the form of a cylindrical block, having in-its upper face a circular pocket 12 receiving a carrier disk 13. Secured to the carrier disk and extending centrally through and journaled in the block 11 is a shaft 14, which at its lower end carries a gear 15, the block being hollow in its lower portion to receive said gear. A gear 16 projects through an opening 17 in the block and meshes with the gear 15. Gear 16 is secured to the upper end of a vertical shaft 18 ournaled in the base and the table and has a worm gear 19 secured to its lower end. Depending from the table 10 are brackets 20 and 21 in which is journaled a shaft 22 carrying a Worm 23, which meshes with the worm gear 19 and a gear 241 which meshes with the pinion 25, this pinion be ing secured to the end of the shaft 26 which is journaled in the frame 21 and which carries the driving pulleys 27 and 28. A driving belt 29, driven by any suitable source of power engages the pulley 27 and thus drives the gearing train for rotating the shaft 14 and the carrier disk 13.

As shown in Fig. 4, the carrier disk has a plurality of suction areas 30 corresponding in outline in a general way to the shape of the pieces to be held by suction, from which suction holes 31 extend downwardly through the disk to the suction pockets 32 cut in the under side of the disk. An arcuate slot or groove 33 is cut in the top surface of the block below the disk and connects with the suction passageway 3a through the block 11, this passageway being connected by a pipe 35 with a suction producing source. Generally speaking, the object of this construction and arrangement is to hold small sheets or'plates of mica against the top of the carrier disk by suction whereby as said carrier revolves, the mica is brought under a suitable grinding wheel which grinds successive sheets to a uniform thickness. Mica sheets of different outlines may be ground in this manner. In Fig. 8, the ordinary U-shaped mica sheets are shown, such as are used in lightning arresters except that their thickness has been exaggerated. To securely hold the mica, the suction holes 31 are arranged in U-form and four suction areas are shown, although any number could be used.

Provision is made for automatically feeding the mica sheets to the carrier disk. As

. shown in Figs. to 8, a vertical chute 36 is supported on brackets 37 above the path of the suction areas, the lower end of the chute being close tothediskand spaced therefrom sufiiciently to permit the exit of only one sheet of mica at a time through the slit thus formed. The thickness of the sheets of mica forming the stack within the chute shown 1n Fig. 8 is exaggerated to make them clearer. Said stack rests on the carrier disk but the lowermost sheet is prevented normally from following the carrier disk by means of a spring 38. This spring is secured to the exit slde of the chute and is bent with 1ts lower well-rounded corner 39 extending downwardly suficiently to be normally 1n front of the lowermost mica sheet, to prevent removal thereof from the chute by its frictional engagement with the rotating carrier disk. At the entrance side of the thute a spring 40 is secured which extends diagonally into the chute, this spring and the diagonal end of the spring 38 serving to gulde the mica plates to the carrier disk. Secured to the carrier disk at the rear ends of the suction areas are the plates 41 forming abut ments which bear successively against the edge of the lowermost mica plates in the chute. Upon such engagement of an abutment with a mica sheet, the latter will be forced underneath the spring 38 and carried away from the chute to the grindingwheel.

Immediately after an abutment engages with the lowermost mica sheet and starts to shift it from the chute, the suction pocket 32 below said mica sheet will come into communication with the suction groove 33 and suction will act through holes 31 to aid in holding said sheet in place. The grinding mechanism is supported on a standard 42 secured to the block 11 at the side thereof. Secured to the front face of the standard 42 above the mica carrier disk is a bearing structure comprising the base 43 and the upper and lower vertical bearing sections 44 and 45, the bearing structure being vertically adjustable on the standard by the slots 46 in the base 43 receiving the screws 47. Extending through the bearing sections 44 and 45 is a bushing 48 which is threaded between the two bearing sections to receive an adjusting nut 49. Journaled in this bushinsane? ing is an arbor 50 to the upper end of which is secured the pulley 51. A drive belt 52 passes around this-pulley and over the guide pulleys 53 and 54 to the drive pulley 28 on the shaft 26. Secured to the lower end of the arbor 50 is the grinding wheel 55. As the disk 13 is slowly rotated to carry mica sheets beneath the grinding wheel, the latter is rapidly rotated and the mica plates are round down to suitable gage. The rinding wheel and shaft are held suspen ed in the bushin 48 by the engagement of the ulley 51 wit the upper end of the bushing. Vertical adjustment of the grinding wheel can be made by means of the screws and slots 47 and 46 and by means of the adjusting nut 49. By loosening the screws 47 the entire bearing structure can be raised or lowered and by turning the nut 49 the bushing 48 can be raised or lowered in the bearing frame and micrometer adjustment of the grind wheel effected. The lower bearing section 45 may be split and a clamping screw 56 provided in order that the bushing 48 may be rigidly clamped to the bearing frame after micrometer adjustment by the nut 49.

It will be noted that the suction groove 33 extends substantially from the rear end of the suction area below the mica chute to a point beyond the range of the grinding wheel. The suction is therefore first applied to a mica sheet when it is engaged by one of the abutments and said suction is maintained until it has passed the grinder. Shortly after the mica sheets leave the grinder, the suction pockets are disconnected from the suction groove 33 and said sheets are released after which they may be readily removed from the carrier disk by the operator. If desired, a pipe 57 may be provided to supply a stream of compressed air to the carrier to blow the released mica plates therefrom.

Although the carrier table and the grindingwheel in the embodiment of the inven-' tion herein illustrated have been shown mounted for rotation on vertical axes, it is obvious they may be otherwise mounted,if desired. Other changes and modifications may also be made in the construction herein illustrated without departing from the sprit of the invention.

What is claimed is: g

1. In a device of the class described, a rotatable carrier havin a plurality of suction areas thereon all 0 which are uniformly disposed with respect to the axis of rotation, and a grinding wheel arranged to rotate adjacent to said carrier and in the path of rotation of said areas. I

2. In a device of the class described, a carrier rotatable about a vertical axis and having a plurality of suction areas thereon formed by perforations therethrough, an abutment at the rear of each of said areas, a

grinding wheel above said carrier adjacent to the path of rotation of said areas, and means for adjusting said rinding wheeltoward and away from saif carrier.

3. In a device of the class described, a chute for sheet mica blanks, a rotatable carrier adjacent to the discharge end of said chute, the lower end of said chute being spaced from said carrier a distance less than the thickness of one of said blanks, a grinding wheel having its operative surface above said carrier a distance less than the thickness of one of said blanks, an abutment on said carrier adapted to pass beneath the discharge end of said chute, said grinding wheel and abutment being arranged at substantially equal distances from said axis of rotation, said abutment having a thickness less than one of said blanks whereby it may engage the lowermost blank in said chute and forcibly push it therefrom to said grinding wheel whereby all of said blanks are ground to uniform thickness, one after the other.

4. A grinding machine having a carrier rotating in a, horizontal plane, a plurality of recesses in the under side of said carrier, equally spaced from the axis of rotation, said recesses communicating with the surface of said carrier by a plurality of perforations constituting suction areas, a support for said carrier, and a port in the upper surface thereof 'with which said recesses cooperate to render the suction available along a predetermined path of travel during the rotation of said suction areas.

5. A grinding machine having a carrier rotating in a horizontal plane, a plurality of recesses in the under side of said carrier equally spaced from the axis of rotation, said recesses communicating with the surface of said carrier by a plurality of perforations constituting suction areas, a support for said carrier, a port in the upper surface thereof with which said recesses cooperate to render the suction available along a predetermined path of travel in the rotation of said suction areas, a chute for feeding blanks to said rotating carrier at the point where such suction becomes available, and a grinding wheel for grinding said blanks before said suction is discontinued.

6. In a device of the class described, a rotatable carrier a chute for feeding mica blanks to the upper surface thereof, means for applying suction to said blanks to hold them to said carrier, a grinding Wheel beneath which said blanks are moved by said carrier to grind them to a uniform thickness, and means for blowing said blanks from said carrier after the grinding operation.

7. In a device of the class described, a rotatable carrier, a grinding wheel mounted thereabove, means whereby a blank may be held on said carrier by suction during its passage beneath said grinding wheel, and

"means whereby said suction is automatically released after the passage of said blank beneath said grinding Wheel.

8. In a device of the class described, a rotatable carrier, a grinding wheel mounted thereabove, means whereby blanks may be held on said carrier by suction during their passage beneath said grinding wheel one at a time, means whereby said suction is released after their passage beneath said grinding wheel, and means for blowing said blanks from said carrier after the release of said suction.

9. In a device of the class described, a carrier rotatable about a vertical axis and having a plurality of suction areas thereon, a grinding wheel above said carrier, a spindle therefor, a support for said spindle having a plurality of bearings, a bushing extending through said bearings, means cooperating with said bushing whereby said grinding wheel may be adjusted relatively to said carrier and to said bearings, and means whereby said support may be adjusted.

10 In a device of the class described, a carrier having a plurality of suction areas thereon, all of which are uniformly dis posed about a common center, a grinding wheel arranged to rotate adjacent to said carrier, and means causing relative rotation of said carrier and said grinding wheel, the axis of rotation passing through said common center whereby said grinding wheel is brought into operative position over said areas in succession.

11. In a device of the class described, a support for the blanks, means for supplying blanks thereto, grinding means arranged ad acent to said support, and means causmg relative rotation of said support with respect to said supplying and grinding means, said support having suction areas for holding said blanks in place upon delivery thereof from said supplying means and until operated on by said grinding means.

12. In a device of the class described, a support for the blanks, a magazine for said blanks, means for feeding said blanks from said magazine to said support one at a time, grinding means arranged adjacent to said support, and means causing relative rotation of said support with respect to said magazine and grinding means, said support having suction areas for holding said blanks in place upon delivery thereof from said magazine and until they are operated on by said grinding means, and means for removing said blanks from said suction areas.

13. A grinding machine having a rotatable carrier, with an opening therethroug h to provide a suction area on said carrier, a stationary member in contact with said carrier having a port arranged to cooperate said carrier to render said suction area operative during part of sa1d rotation, grinding means located adjacent to the path of rotation of said suction area to grind the blank held thereon, and means for rotating said carrier.

14. A grinding machine having a rotatable carrier with openings therethrough provided a plurality of suction areas on said carrier, a stationary member in contact with said carrier having a port arranged to cooperate with said openings during the rotation of said carrier to render said suction areas operative during a predetermined part of said rotation, means for supplying blanks, one at a time, to said areas, grinding means located adjacent to the path of rotation of said suction areas to grind the blanks held thereon, and means for rotating said carrier.

15. A grinding machine having a rotatable carrier with an opening therethrough to provide a suction area thereon, a support for said carrier having a port arranged to cooperate with said opening during the romeans? tation of said carrier to render said suction area operative during part of said rotation, grinding means mounted adjacent to the path of rotation of the blank held on said carrier by said suction area, means in addition to said suction area for holding said blank in place, and means for rotating said carrier. I

16. A grinding machine having a rotatable carrier with openings therethrough providing a plurality of suction areas on said carrier, a stationary member in contact with said carrier having a port arranged to cooperate with said openings during the rotation of said carrier to render said suction areas operative during a predetermined part of said rotation, a magazine for the blanks to be operated on, means for feeding said blanks from said magazine to said carrier one at a time, grinding means located adjacent to the path of rotation of said suction areas to grind the blanks held thereon, and means for rotating said carrier.

In witness whereof, I hereunto subscribe my name this 22nd day of July, A. D. 1916.

JAMES T. GRIFFIN. 

